Make telemetry strictly opt-in then, that's really the only respectful way to do it.
Everything else is sophistry.
Not singling you out either, too many projects do it by default, yours at least makes it obvious here that you do and how to turn it off https://authzed.com/docs/spicedb/ops/observability#telemetry so kudos for not hiding it in the basement behind a "Beware of the Leopard" sign.
For open source projects I just find it more offensive, I'd expect closed source projects to do it by default (but I expect less of them to start with) but for open source it rankles much more.
You didn't explain why, in your opinion, opt-out is disrespectful; why respect requires opt-in. For most Western users, the bandwidth is hardly a drop in the bucket, and while there are certainly kinds of telemetry that are disrespectful of a user's privacy, telemetry in and of itself is not (in my opinion) abusive of user privacy, and therefore neither is opt-out abusive.
Indeed, if you were to argue that telemetry violates user privacy, then opt-in (i.e. to help send bug reports) doesn't fix that. If you add a "send bug report" button, but the data collected in the bug report abuses the user's privacy, why is it ethically any better? The data collected is far more important than the frequency or control over how and when it's sent. Users who desire taking that control should anyway run their own restrictive, allowlist-based firewall, which no opt-in/opt-out setting can overcome anyway.
With opt-in on an open-source project I get to choose to help contributing something back (telemetry data) to help the project.
Opt-out telemetry is not compatible with respect. It also adds an obstacle when I try to advocate the software to friends and coworkers. I have to warn them about it in advance, which is often where it ends because we’ve been burned in the past with other software adding extra things to their telemetry that weren’t there before, or changing the name of the environment variable that disables telemetry, or someone on the team does something that accidentally causes data to be transmitted unintentionally.